Exhaust system for a combustion engine

ABSTRACT

An exhaust system for a combustion engine having a plurality of cylinders, a cylinder head and an engine block is provided. The exhaust system comprises an exhaust manifold, which is integrated in the cylinder head, flow channels, and an exhaust pipe, which is connected to a head flange of the cylinder head. The flow channels each extend from one of the cylinders to a head flange. At least two of the flow channels, which are connected to cylinders that are not ignited in succession, are united within the cylinder head and form a common flow channel. At least one further flow channel, which is connected with a cylinder ignited in succession, is routed separately as far as to the head flange. The common flow channel is united with the further flow channel only in the exhaust pipe.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to German Patent Application No. 10 2011 116 360.7, filed Oct. 19, 2011, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This application pertains to a combustion engine that is equipped with an exhaust system with which exhaust gases that are created in the combustion engine or in cylinders of the combustion engine are discharged. The exhaust gases are conducted from the respective cylinders via an exhaust manifold up to a common outlet and thereafter into a catalytic converter, wherein undesired components of the exhaust gases are removed or converted into non-toxic substances.

BACKGROUND

The exhaust manifold can be produced as a separate component that is mounted to the cylinder head of the combustion engine by means of bolts or the like. The exhaust manifold is arranged freely positioned towards the atmosphere and designed as an element that is separate from the cylinder head, so that the exhaust manifold cannot be cooled by means of a cooling water jacket, but by means of the ambient air. Since the exhaust manifold is mounted separately to the engine, the mounting costs can increase however. The tight space in the engine compartment limits the technical configuration possibilities of the exhaust manifold.

The Publication DE 10 2008 058 852 A1 discloses an exhaust system of a combustion engine, wherein the cylinder head the exhaust manifold are designed integrally. This arrangement has the advantage that the assembly is simplified and the spatial utilization of the engine compartment is improved. It is possible, however, that because of the compact design the exhaust gas resistance and the fuel consumption increase. In order to prevent this problem, DE 10 2008 058 852 A1 discloses that the individual passages from the cylinders as far as to the exhaust gas flange in the cylinder head are arranged so that fewer turbulences and a lower flow resistance are achieved. Consequently the fuel consumption can be reduced.

Further improvements in the case of exhaust gas systems for combustion engines are desirable however in order to further reduce the fuel consumption. In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.

SUMMARY

An exhaust system for a combustion engine having a plurality of cylinders, a cylinder head and an engine block is stated, which comprises an exhaust manifold that is integrated in the cylinder head and a further exhaust pipe, which is connected to a head flange of the cylinder head. The exhaust manifold, which is integrated in the cylinder head, has flow channels which in each case extend from one of the cylinders to the head flange. At least two of the flow channels, which are connected to cylinders which are not ignited one after the other in a firing order are united within the cylinder head and form a common flow channel. At least one further flow channel, which is connected to a cylinder that is ignited one after the other in the firing order, is routed separately as far as to the head flange. The common flow channel is only united with the further flow channel in the exhaust pipe.

The exhaust system according to the present disclosure is thus partly integrated within the cylinder head and partly arranged outside the cylinder head as with a separate exhaust manifold. For example, two flow channels of cylinders, which are arranged not following one after the other in the firing order, are united within the cylinder head. In contrast with this, at least one flow channel of a cylinder, which is ignited one after the other in the firing order, is only connected outside the cylinder head in the exhaust pipe with the flow pipe of at least one cylinder, which follows one after the other in the firing order. The terms outlet system and exhaust system, outlet manifold and exhaust manifold are synonymous.

This arrangement has the advantage that the length of the flow channel of cylinders ignited one after the other is extended compared with an integrated exhaust manifold. This results in an improved separation of the exhaust gas pulses, a lower residual gas content and a performance and torque increase compared with an exhaust manifold with which all flow channels are interconnected in the cylinder head.

For example, a typical firing order in the case of a four-cylinder combustion engine is I-III-IV-II. In this example, the flow channels from the cylinders I and IV can be united in the cylinder head and the flow channel of cylinder II and III can be united with the common flow channel of the cylinder I and IV only outside the cylinder head downstream of the head flange within the exhaust pipe.

In an exemplary embodiment, the further flow channel is connected to the common flow channel downstream of the cylinder head flange. The further flow channel is connected to a cylinder, is united in succession with one of the cylinders that is connected to the common flow channel only downstream of the head flange. Thus, the length of the flows from the cylinders up to a point at which the exhaust gas of two cylinders following in succession is united, is increased. Consequently, because of the additional exhaust pipe, the exhaust gas pulses of two cylinders following in succession are better separated from each other.

In another exemplary embodiment, a third flow channel is provided, which extends from a cylinder which in the firing order follows one of the two cylinders in succession, which are connected to the common flow channel. The third flow channel is connected to the common flow channel only downstream of the cylinder head.

For example, in a four-cylinder combustion engine having a firing order of I-III-IV-II the flow channels from the cylinders I and IV are united in the cylinder head and the flow channel of cylinder II and the flow channel of cylinder III are united with the common flow channel of the cylinders I and IV only outside the cylinder head downstream of the head flange within the exhaust pipe.

The flow channel of the cylinder III, can be connected to the common flow channel of the cylinders I, IV and II further downstream of the point at which the flow channel of cylinder II is connected to the common flow channel of the cylinders I and IV. Alternatively, the flow channel from the cylinder III can be connected to the common flow channel I and IV at the same point as the flow channel of the cylinder II.

In an exemplary embodiment, the exhaust pipe comprises at least two separate flow branches which are united in order to form a combined flow branch. The two separate flow branches are arranged upstream and the combined flow branch is arranged downstream. One of the flow branches is connected to the common flow channel and the other flow branch is connected to the further flow channel of the exhaust manifold integrated in the cylinder head. Thus, the two flow branches extend the length of the separation of the exhaust gas flows of cylinders ignited in succession.

In an exemplary embodiment, the exhaust pipe comprises a separating wall at an inlet end, wherein two separate flow channels or flow branches are formed.

The exhaust pipe comprises at least two inlet flow channels and a single common exhaust flow channel, which is connected to the inlet flow channels. The number of the inlet flow channels corresponds to the number of the flow channels which are arranged on the head flange of the cylinder head separately from one another.

In an exemplary embodiment, the exhaust pipe comprises an inlet flange having at least two inlet openings, an exhaust flange having an exhaust opening and flow channels. The inlet flange is connected to the head flange of the integrated exhaust manifold and the flow channels each extend from one of the inlet openings as far as to the exhaust opening. The flow channels from the inlet openings are separate from one another for a predetermined distance in the direction of the exhaust openings and after this distance united and form a combined flow channel.

The predetermined distance can be predetermined for each engine type, for example the number of the cylinders and the power, in order to optimize the power and further characteristics of the combustion engine. The utilizable space in the engine type can also be taken into account in order to be able to state the optimum power in the predetermined space.

In an additional further development, one of the inlet openings is connected to the common flow channel and one of the inlet openings is connected to the further flow channel in the cylinder head.

In another exemplary embodiment, flow channels of two further cylinders, which are arranged not in succession in a firing order, are united within the cylinder head and form a second common flow channel.

For example, in a four-cylinder combustion engine with a firing order of I-III-IV-II, the flow channels of the cylinders I and IV can form a first common flow channel in the cylinder head and the flow channels of the cylinders II and III can form a second common flow channel in the cylinder head. The two cylinders of each of these pairs of cylinders thus do not follow in succession in the firing order. Cylinders of different pairs by contrast follow in succession. The two common flow channels are separated from each other within the cylinder head and are united only downstream of the cylinder head outside the cylinder head and within an exhaust pipe.

The second common flow channel is connected to the first common flow channel after a predetermined distance downstream of the head flange within the exhaust pipe in order to ensure the desired better separation of the exhaust gas pulses relative to an integrated exhaust manifold.

A combustion engine having a plurality of cylinders, an engine block, a cylinder head and an exhaust system according to any one of the preceding exemplary embodiments is also stated. A vehicle, for example a motor vehicle, having a combustion engine and an exhaust system according to any one of the preceding exemplary embodiments is also stated.

Combined, cylinder heads with integrated exhaust manifold, so-called integrated exhaust manifolds (IEM), make possible cost savings through the omission of the conventional separate manifold, but which are slightly reduced through other additional costs, for example a larger radiator or the more elaborate cylinder head design. The reduction of the surface as far as to the catalytic converter allows a faster heating-up and thus the reduction of emissions. In stationary engine operation, the cooling of the region of the exhaust system integrated in the cylinder head leads to lower exhaust gas temperatures and thus to a lower enrichment need.

The separation of the exhaust gas pulses in the case of a four-cylinder engine in this case is effected through the uniting of the runners of cylinders I and IV as well as cylinders II and III. A conventional 4-1 IEM design of a four-cylinder engine includes that the flow channels of all cylinders are united with the cylinder head. The compact design of an integrated IEM and the absent separation of the exhaust gas pulses can lead to a higher residual gas content and to a loss of power and torque. In contrast with this, conventional external exhaust manifolds for naturally aspirated engines are characterized by long runners.

These problems can be avoided by using an exhaust system according to the present disclosure, wherein the flow channels of two cylinders not following in succession are united within the cylinder head, while the flow channels of the cylinders following in succession are only united outside the cylinder head in an additional exhaust pipe, which is mounted onto the cylinder head flange. Thus, the length of the flow of two cylinders following each other in succession in the firing order until they are united is extended compared with that of an integrated exhaust manifold.

In summary, with the exhaust system according to the present disclosure, the advantages of an exhaust manifold integrated in the cylinder head are combined with those of an excellent gas dynamic and pulse separation of the exhaust stroke with a conventional exhaust manifold. The present disclosure combines the compact design of a 4-1 IEM manifold with the good pulse separation and performance of a conventional exhaust manifold.

Slight performance advantages materialize through a uniting of cylinders I and IV as well as II and III in the cylinder head. However, these can be substantially increased if the channel separation of the two exhaust gas flows is maintained for an additional distance after the head flange. By combining both measures, the performance of the combustion engine can be further improved.

A person skilled in the art can gather other characteristics and advantages of the disclosure from the following description of exemplary embodiments that refers to the attached drawings, wherein the described exemplary embodiments should not be interpreted in a restrictive sense.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:

FIG. 1 shows a schematic top view of a combustion engine with an exhaust system according to an exemplary embodiment;

FIG. 2 shows a perspective view of the exhaust gas-conducting inner surfaces of the exhaust system;

FIG. 3 shows a second perspective view of the exhaust gas-conducting inner surfaces of the exhaust system of FIG. 2;

FIG. 4 shows a cross section of the exhaust system of FIG. 1;

FIG. 5 shows a cross section of an exhaust system according to another exemplary embodiment; and

FIG. 6 shows diagrams of the performance of combustion engines with different exhaust systems.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and is not intended to limit the present disclosure or the application and uses of the present disclosure. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.

FIG. 1 shows a schematic top view of a combustion engine 1 according to an exemplary embodiment. The combustion engine 1 comprises a cylinder head 2, an engine block which is not shown in FIG. 1 and four cylinders 3, 4, 5, 6 which form the combustion spaces.

The four cylinders 3, 4, 5, 6 are each connected to a flow channel 7, 8, 9, 10 of an exhaust system 11, through which exhaust gases from the combustion reaction in the cylinders are conducted to a catalytic converter which is not shown in FIG. 1. The flow channels 7, 8, 9, 10 are integrated in the cylinder head 2 and are part of an exhaust manifold 12, which is integrated in the cylinder head 2. The exhaust system according to the present disclosure however is not restricted to combustion engines having four cylinders and can be used with combustion engines having fewer or more than four cylinders.

In addition to the flow channels 7, 8, 9, 10, which are integrated in the cylinder head 2, the exhaust system 11 comprises an additional exhaust pipe 13 which is mounted on a head flange 14 of the cylinder head 2.

The exhaust pipe 13 comprises an inlet flange 17, which is mounted on the head flange 14 of the cylinder head 2, and an exhaust flange 18, which is connected to further components of the exhaust system, such as a catalytic converter, which are not shown.

The combustion engine 1 comprises four cylinders 3, 4, 5, 6 which are ignited in the firing order I-III-IV-II, i.e. in the order cylinder 3, cylinder 5, cylinder 6, cylinder 4.

The flow channels 7 and 10 of the cylinders 3 and 6, which correspond to the cylinders I and IV of the firing order, are united within the cylinder head 2 and form a first common flow channel 15 on the head flange 14. The flow channels 8 and 9 of the cylinders II and III of the firing order are likewise united within the cylinder head 2 and form a second common flow channel 16 on the head flange 14. The first common flow channel 15 however is separated from the second common flow channel 16 within the cylinder head 2.

The first common flow channel 15 is only connected to the second common flow channel 16 outside the cylinder head 2. Consequently, the exhaust gas flow of the first flow channel 15 is only in contact with the exhaust gas flow of the second common flow channel 16 downstream of the cylinder head 2 and outside the cylinder head 2.

According to the present disclosure, flow channels of cylinders not ignited in succession are interconnected within the cylinder head 2. Flow channels of cylinders ignited in succession are interconnected downstream of the cylinder head 2.

Flows of exhaust gases from cylinders which are ignited in succession in the firing order meet only downstream of the cylinder head 2 within the additional exhaust pipe 13 since the two common flow channels 15, 16 are separated within the cylinder head 2 and are interconnected only after a predetermined length 1 within the exhaust pipe 13.

Consequently, the exhaust gas pulses of cylinders ignited in succession only meet downstream of the head flange 14 after a length 1. The exhaust pipe 13 provides a kind of extension piece for the integrated exhaust manifold 12.

The FIGS. 2 and 3 show perspective views of the exhaust-gas conducting inner surfaces of the exhaust system 1. FIG. 2 shows a perspective top view and FIG. 3 a perspective lateral view. In the FIGS. 2 and 3 it is shown that each flow channel 7, 8, 9, 10 of the exhaust manifold 12 has two branches 7′, 7″, 8′, 8″, 9′, 9″, 10′, 10″, each of which is connected to one of two exhaust openings of the respective cylinders 3, 4, 5, 6.

These two branches 7″, 8′, 8″, 9′, 9″, 10′, 10″ are united within the cylinder head 2 and upstream of the start of the common flow channels 15, 16 of the cylinder head 2. In the FIGS. 2 and 3, the head flange, which forms the boundary between the integrated exhaust manifold 12 and the additional exhaust pipe 13, is graphically represented by a line 14.

FIGS. 2 and 3 show that on the head flange 14 the flow channels 7 and 10 of the cylinders 3 and 6, which correspond to the cylinders of the firing order I and IV and are united in the common flow channel 15, below the flow channels 8 and 9 of the cylinders 4 and 5, which correspond to the cylinders II and III of the firing order, and of the second common flow channel 16.

FIG. 3 graphically shows that the exhaust pipe 13 comprises two separate branches 19, 20 on the inlet end 21 of the exhaust pipe 13. These two separated branches 19, 20 are united within the exhaust pipe 12 only after a predetermined distance 1 in order to form a combined flow pipe 21. The exhaust gas flow from the cylinders I and IV in the firing order, i.e. cylinders 3, 6, are kept separate from the flow from the cylinders II and III, i.e. cylinders 4, 5 even outside the cylinder head 2. The flow length of the exhaust gases of cylinders ignited in succession is thus extended with the help of the exhaust pipe 13.

The position of the joining of the flow channels 7 and 10 within the cylinder head is graphically shown with the line 15 and the joining of the flow channels 8 and 9 with the line 16 in FIG. 3.

FIG. 4 shows a schematic cross section of the connection between the cylinder head 2, in particular of the head flange 14 and the exhaust pipe 13.

The inlet flange 17 of the exhaust pipe 13 comprises two inlet openings 22, 23 and the exhaust flange 18 a single outlet opening 24. The two inlet openings provide for two flow channels 19, 20 within the exhaust pipe 13, which extend separately from each other for a predetermined distance in the direction of the exhaust opening 21. Following this predetermined distance, the flow channels 19, 20 are united and form a combined flow channel 21. The transition from the separated flow channels 19, 20 to the combined flow channel 21 is shown with the line 25 in FIG. 3.

One of the inlet openings 22 is connected to the first common flow channel 15 of the cylinder head 2 and the second inlet opening 23 is connected to the second common flow channel 16 of the cylinder II. Consequently, exhaust gas flow of cylinders fired in succession only meet at the point that that is designated with the line 25.

FIG. 5 shows a cross section of a part of an exhaust system 11′ according to another exemplary embodiment. The exhaust system 11′ according to this exemplary embodiment differs from the exhaust system 1 of the prior exemplary embodiment by the design of the exhaust pipe 13. In contrast with the prior exemplary embodiment, the two flow channels 19, 20 within the exhaust pipe 13′ are formed through a single separating wall 26.

FIG. 6 shows diagrams of torque and residual gas content as a function of the rotational speed for a 1.81 naturally aspirated engine having five different exhaust manifolds, namely an external manifold design of an engine (square), two differently embodied 4-1 IEM designs (circle and diamond), as well as two designs of an IEM with united runners ¼ and ⅔ (triangle). An exhaust manifold according to the present disclosure for this certain engine on the basis of a 4-2-1 concept in this case is characterized by a 35 mm long continuation of the separating wall beyond the head flange. The length of the continuation is system-dependent.

The use of an integrated exhaust manifold for a naturally aspirated engine, for example with a 1.81 engine, can result in performance losses of up to 2 kW and 4 Nm compared with an external exhaust manifold. The exhaust system according to the present disclosure makes possible a performance that corresponds to the performance of an external exhaust manifold even with a more compact installation space.

While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the present disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the present disclosure as set forth in the appended claims and their legal equivalents. 

What is claimed is:
 1. An exhaust system for a combustion engine having a plurality of cylinders, a cylinder head and an engine block, the exhaust system comprising: an exhaust manifold integrated in the cylinder head; a plurality of first flow channels, which each extend from one of the cylinders to a head flange, at least two of the plurality of first flow channels are connected to cylinders which are not ignited in succession in a firing order, and are united within the cylinder head to form a common flow channel; a second flow channel, which is connected to a cylinder that is ignited in succession in the firing order and is conducted separately as far as to the head flange; and an exhaust pipe that is connected to the head flange, wherein the common flow channel is united with the second flow channel only in the exhaust pipe.
 2. The exhaust system according to claim 1, wherein the second flow channel is connected to the common flow channel downstream of the head flange.
 3. The exhaust system according to claim 1, wherein a third flow channel of a cylinder, which follows one of the two cylinders in succession in the firing order is connected to the common flow channel downstream of the cylinder head.
 4. The exhaust system according to claim 1, wherein the exhaust pipe comprises at least two separate flow channels.
 5. The exhaust system according to claim 1, wherein the exhaust pipe comprises a separating wall at an inlet end, wherein two separate inlet flow channels are formed.
 6. The exhaust system according to claim 5, wherein the exhaust pipe comprises at least two inlet flow channels and a single common exhaust flow channel, which is connected to the inlet flow channels.
 7. The exhaust system according to claim 6, wherein the exhaust pipe comprises an inlet flange having at least two inlet openings, an exhaust flange with an exhaust opening, and inlet flow channels, wherein the inlet flange is connected to the head flange of the integrated exhaust manifold, and the inlet flow channels each extend from one of the inlet openings as far as to the exhaust opening, wherein the inlet flow channels from the inlet openings are separated from each other for a predetermined distance in the direction of the exhaust opening and after this distance are united and form a combined flow channel.
 8. The exhaust system according to claim 7, wherein one of the inlet openings is connected to the common flow channel and one of the inlet openings to the second flow channel.
 9. The exhaust system according to claim 1, wherein two of the plurality of first flow channels of two further cylinders, which do not follow in succession in the firing order, are united within the cylinder head and form a second common flow channel.
 10. The exhaust system according to claim 9, wherein the second common flow channel is connected to the first common flow channel after a predetermined distance downstream of the head flange within the exhaust pipe.
 11. A combustion engine having an engine block, the combustion engine comprising: a plurality of cylinders having a cylinder head; and an exhaust system, including: an exhaust manifold integrated in the cylinder head; a plurality of first flow channels, which each extend from one of the cylinders to a head flange, with two of the plurality of first flow channels connected to cylinders which are not ignited in succession in a firing order and are united within the cylinder head to form a first common flow channel, and two of the plurality of first flow channels of two further cylinders, which do not follow in succession in the firing order, are united within the cylinder head and form a second common flow channel; a second flow channel, which is connected to a cylinder that is ignited in succession in the firing order and is conducted separately as far as to the head flange; and an exhaust pipe that is connected to the head flange, wherein the first common flow channel is united with the second flow channel only in the exhaust pipe.
 12. The combustion engine according to claim 11, wherein the second flow channel is connected to the first common flow channel downstream of the head flange.
 13. The combustion engine according to claim 11, wherein the exhaust pipe comprises at least two separate flow channels.
 14. The combustion engine according to claim 11, wherein the exhaust pipe comprises a separating wall at an inlet end, wherein two separate inlet flow channels are formed.
 15. The combustion engine according to claim 14, wherein the exhaust pipe comprises at least two inlet flow channels and a single common exhaust flow channel, which is connected to the inlet flow channels.
 16. The exhaust system according to claim 15, wherein the exhaust pipe comprises an inlet flange having at least two inlet openings, an exhaust flange with an exhaust opening, and inlet flow channels, wherein the inlet flange is connected to the head flange of the integrated exhaust manifold, and the inlet flow channels each extend from one of the inlet openings as far as to the exhaust opening, wherein the inlet flow channels from the inlet openings are separated from each other for a predetermined distance in the direction of the exhaust opening and after this distance are united and form a combined flow channel.
 17. The exhaust system according to claim 16, wherein one of the inlet openings is connected to the first common flow channel and one of the inlet openings to the second flow channel.
 18. A vehicle having a combustion engine, the vehicle comprising: a combustion engine including a plurality of cylinders each having a cylinder head; and an exhaust system, including: an exhaust manifold integrated in the cylinder head; a plurality of first flow channels, which each extend from one of the cylinders to a head flange, with two of the plurality of first flow channels connected to cylinders which are not ignited in succession in a firing order and are united within the cylinder head to form a first common flow channel, and two of the plurality of first flow channels of two further cylinders, which do not follow in succession in the firing order, are united within the cylinder head and form a second common flow channel; a second flow channel, which is connected to a cylinder that is ignited in succession in the firing order and is conducted separately as far as to the head flange; and an exhaust pipe that is connected to the head flange, wherein the first common flow channel is united with the second flow channel only in the exhaust pipe, and the second flow channel is connected to the first common flow channel downstream of the head flange.
 19. The combustion engine according to claim 18, wherein the exhaust pipe comprises at least two separate flow channels. 